U.S. patent number 5,824,027 [Application Number 08/911,604] was granted by the patent office on 1998-10-20 for nerve cuff having one or more isolated chambers.
This patent grant is currently assigned to Simon Fraser University. Invention is credited to Yunquan Chen, Paul Richard Christensen, Joaquin Andreas Hoffer, Kevin D. Strange.
United States Patent |
5,824,027 |
Hoffer , et al. |
October 20, 1998 |
Nerve cuff having one or more isolated chambers
Abstract
A nerve cuff has one or more sets of electrodes for selectively
recording electrical activity in a nerve or for selectively
stimulating regions of the nerve. Each set of electrodes is located
in a longitudinally extending chamber between a pair of
longitudinal ridges which project into the bore of the nerve cuff.
The ridges are electrically insulating and serve to improve the
selectivity of the nerve cuff. The ridges seal against an outer
surface of the nerve without penetrating the nerve. Nerve cuffs
according to the invention may be used in functional electrical
stimulation systems. Electrodes may be replaced with fine tubes to
enable pharmacological agents to be delivered selectively through
the tubes to portions of a nerve passing through the cuff or to
permit the sampling of fluids from regions adjacent selected outer
portions of the nerve. The nerve cuff may be constructed of modular
segments which can be selected to provide a customized fit to the
shape and size of a nerve at time of implantation.
Inventors: |
Hoffer; Joaquin Andreas
(Anmore, CA), Chen; Yunquan (Vancouver,
CA), Strange; Kevin D. (Port Moody, CA),
Christensen; Paul Richard (Burnaby, CA) |
Assignee: |
Simon Fraser University
(Burnaby) N/A)
|
Family
ID: |
25430551 |
Appl.
No.: |
08/911,604 |
Filed: |
August 14, 1997 |
Current U.S.
Class: |
607/118;
600/377 |
Current CPC
Class: |
A61N
1/0556 (20130101) |
Current International
Class: |
A61N
1/05 (20060101); A61N 001/05 () |
Field of
Search: |
;607/118,148
;600/372,373,377,393 ;604/93,179,20,174,175,280,264 |
References Cited
[Referenced By]
U.S. Patent Documents
Other References
Hoffer et al., "Neural signals for Command Control and Feedback in
Functional Neuromuscular Stimulation: A Review", Journal of
Rehabilitation Research and Development, vol. 33, No. 2, Apr. 1996,
145-157. .
Goodall et al., "Position-Selective Activation of Peripheral Nerve
Fibers With a Cuff Electrode", IEEE Transactions On Biomedical
Engineering, vol. 43, No. 8, Aug. 1996, 851-856..
|
Primary Examiner: Kamm; William E.
Assistant Examiner: Schaetzle; Kennedy J.
Attorney, Agent or Firm: Oyen Wiggs Green & Mutala
Claims
What is claimed is:
1. A nerve cuff comprising:
(a) an electrically insulating tubular cuff body of a biocompatible
material penetrated by a bore for receiving a nerve, the cuff body
having a closure for permitting passage of a nerve into the
bore;
(b) a plurality of electrically insulating blunt longitudinal
ridges extending generally longitudinally on an inner surface of
the cuff body and projecting into the bore, adjacent pairs of the
longitudinal ridges defining a plurality of chambers extending
generally longitudinally in the bore; and,
(c) an electrode in each of a plurality of the chambers, the
electrode located between a pair of adjacent ones of the
longitudinal ridges.
2. The nerve cuff of claim 1 wherein each of the longitudinal
ridges comprises a soft pliable material.
3. The nerve cuff of claim 2 wherein each of the longitudinal
ridges comprises an elongated tubular member.
4. The nerve cuff of claim 3 wherein the longitudinal ridges extend
along substantially an entire length of the cuff body.
5. The nerve cuff of claim 4 wherein the tubular member has a wall
having a thickness in the range of 0.05 mm to 0.25 mm.
6. The nerve cuff of claim 1 wherein the longitudinal ridges extend
substantially an entire length of the cuff body.
7. The nerve cuff of claim 6 comprising first and second
circumferential sealing ridges at first and second ends of the bore
wherein the longitudinal ridges extend between the first and second
circumferential sealing ridges.
8. The nerve cuff of claim 7 wherein each of the longitudinal
ridges has a generally semi-circular cross sectional profile.
9. The nerve cuff of claim 6 wherein the longitudinal ridges
project into the bore by approximately 5% to 20% of an internal
diameter of the bore.
10. The nerve cuff of claim 9 comprising a set of three spaced
apart electrodes arranged in a line along each chamber midway
between each pair of adjacent ones of the longitudinal ridges.
11. The nerve cuff of claim 10 wherein two outermost ones of the
electrodes in each chamber are electrically shorted together.
12. The nerve cuff of claim 10 wherein the closure comprises a pair
of spaced apart first apertured members affixed to the cuff body at
a first edge of a slit in the cuff body, the first apertured
members having apertures aligned generally with the slit; a second
apertured member capable of being interdigitated between the first
apertured members and affixed to the cuff body at a second edge of
the slit, the second apertured member having an aperture aligned
generally with said slit; and an elongated locking member capable
of being inserted to extend through the apertures of the first
apertured members and the second apertured member when the second
apertured member is interdigitated with the first apertured
members.
13. The nerve cuff of claim 1 wherein the cuff body comprises a
self curling sheet biased to curl about an axis and the
longitudinal ridges extend generally parallel to the axis.
14. The nerve cuff of claim 1 wherein the cuff body comprises a
plurality of linked segments, each of the segments comprising a
cuff body portion bearing a longitudinally extending blunt ridge
member, each segment spanning a portion of a circumference of the
nerve cuff.
15. The nerve cuff of claim 14 wherein the ridge member on each
segment comprises a curved flap extending from the cuff body
portion.
16. The nerve cuff of claim 15 wherein the curved flap on each
segment extends along a lateral edge of the segment and overlaps a
closure linking the segment to an adjacent segment.
17. The nerve cuff of claim 16 wherein the curved flap is spaced
slightly inwardly from the closure.
18. The nerve cuff of claim 17 wherein the closure comprises two or
more spaced apart first apertured members affixed to the first
lateral edge of a first adjacent segment, the first apertured
members having apertures aligned generally with the first lateral
edge of the first segment; one or more second apertured members
capable of being interdigitated between the first apertured members
and affixed to a second lateral edge of a second adjacent segment,
the second apertured members having apertures aligned generally
with the second lateral edge of the second adjacent segment; and an
elongated locking member capable of being inserted to extend
through the apertures of the first apertured members and the second
apertured members when the second apertured members are
interdigitated with the first apertured members.
19. A nerve cuff comprising:
(a) fluid impermeable tubular cuff body penetrated by a bore for
receiving a nerve, the cuff body having a closure for permitting
passage of a nerve into the bore;
(b) a plurality of fluid impermeable rounded longitudinal ridges
extending generally longitudinally on an inner surface of the cuff
body and projecting into the bore, adjacent pairs of the
longitudinal ridges defining a plurality of chambers extending
generally longitudinally in the bore; and,
(c) a plurality of tubes, each one of the plurality of tubes
extending into a different one of a plurality of the chambers for
carrying fluid into or out of the chamber.
20. The nerve cuff of claim 19 comprising two or more tubes
extending into each of one or more of the chambers.
21. The nerve cuff of claim 19 wherein each of the longitudinal
ridges comprises an elongated tubular member.
22. The nerve cuff of claim 21 wherein the longitudinal ridges
extend substantially an entire length of the cuff body.
23. The nerve cuff of claim 21 wherein the tubular member has a
wall having a thickness in the range of 0.05 mm to 0.25 mm.
24. The nerve cuff of claim 19 comprising first and second
circumferential sealing ridges at first and second ends of the bore
wherein the longitudinal ridges extend between the first and second
circumferential sealing ridges.
25. The nerve cuff of claim 24 wherein each of the longitudinal
ridges has a generally semi-circular cross sectional profile.
26. The nerve cuff of claim 24 wherein each of the longitudinal
ridges has a generally circular cross sectional profile.
27. A nerve cuff comprising:
(a) a segment comprising a cuff body wall portion;
(b) first and second longitudinally extending blunt ridge members
extending along the cuff body wall portion and defining an
open-sided chamber extending between the first and second
ridges;
(c) a band member connectible between first and second sides of the
cuff body wall portion to define a bore; and,
(d) one or more electrodes or one or more fluid conduits extending
into the chamber;
wherein the band member is capable of holding the cuff body wall
portion to a nerve passing through the bore with the ridges sealing
against an outer surface of the nerve and the nerve closing the
open side of the chamber.
28. A method for selectively interfacing to a nerve, the method
comprising the steps of:
(a) providing a nerve cuff, the nerve cuff comprising:
(i) a tubular cuff body penetrated by a bore for receiving a nerve,
the cuff body having a closure for permitting passage of a nerve
into the bore;
(ii) a plurality of longitudinal ridges extending generally
longitudinally on an inner surface of the cuff body and projecting
into the bore, adjacent pairs of the longitudinal ridges defining a
plurality of chambers extending generally longitudinally in the
bore; and,
(iii) in at least one of the chambers, an interface comprising at
least one electrode or at least one fluid port;
(b) dissecting a nerve from surrounding tissues;
(c) opening the closure and placing the cuff around the nerve with
the chambers extending along portions of the nerve;
(d) closing the closure, thereby bringing the ridges into sealing
contact with an outer surface of the nerve without penetrating the
outer surface of the nerve; and,
(e) either stimulating selected portions of the nerve by
introducing electrical signals via the at least one electrode or
pharmacological agents via the at least one fluid port into
selected ones of the chambers or monitoring selected portions of
the nerve by measuring electrical potentials in the chambers or
sampling fluids from the chambers.
Description
TECHNICAL FIELD
This invention relates to biomedical apparatus and, in particular
to implantable nerve cuffs for stimulating nerves and/or recording
electrical activity in nerves. The invention is particularly
applicable to nerve cuffs equipped with electrodes for stimulating
and/or monitoring electrical activity in nerve tissues in human
beings or other creatures possessing nervous systems. Nerve cuffs
according to the invention may have particular application in
functional electrical stimulation ("FES") of the neuromuscular
system. This invention may also be used in implantable biomedical
devices for introducing, monitoring or removing fluids or other
matter from the vicinity of nervous tissues.
BACKGROUND
Nerve cuffs equipped with electrodes may be used for interfacing
with the nervous system by recording from or stimulating neural
tissues. For example, implanted nerve cuffs have been used to
record nerve signals from peripheral nerves in animals in a wide
range of experimental conditions. A nerve cuff comprises a tube of
a suitable biocompatible material having a bore and a
longitudinally extending closure. The bore of the nerve cuff has a
diameter which is generally slightly larger than the diameter of
the nerve which the cuff will be applied to.
A nerve cuff is surgically implanted around a nerve. Very
generally, this is done by dissecting a portion of the nerve away
from other tissues, opening the closure of the nerve cuff, placing
the nerve cuff around the dissected portion of the nerve and then
sealing the closure so that the nerve passes through the bore of
the nerve cuff. Electrodes inside the bore may be used to stimulate
the nerve, monitor electrical activity in the nerve and/or measure
impedance or other electrical characteristics of the nerve. Small
tubes may be used to carry fluids, such as medicines into the nerve
cuff or to remove fluid samples from within the nerve cuff.
Kalles.o slashed.e et al., U.S. Pat. No. 5,487,756 entitled
IMPLANTABLE CUFF HAVING IMPROVED CLOSURE describes a nerve cuff of
a type which may be used for stimulating or monitoring electrical
activity in nerves.
Nerve cuff electrodes have been used in stimulation systems with
the goal of providing partial voluntary control of muscles that
have been paralysed as a result of lesions caused by spinal cord
injury, stroke, or other central neurological system disorders. In
some cases, partial motor function can be restored by stimulating
motor neurons or muscles below the level of the lesion. Nerve cuffs
may also be used as sources for feedback for the control of
closed-loop functional electrical stimulation (FES) systems, for
example, the system described in Hoffer, U.S. Pat. No. 4,750,499
entitled CLOSED-LOOP IMPLANTED SENSOR, FUNCTIONAL ELECTRICAL
STIMULATION SYSTEM FOR PARTIAL RESTORATION OF MOTOR FUNCTIONS.
Hoffer et al., Neural signals for command control and feedback in
functional neuromuscular stimulation: a review J. Rehab. Res &
Dev. 33:145-157, 1996 reviews the recent developments in the field
of FES.
Recently, nerve recording cuff electrodes have been implanted
around small nerves in either the hands or legs of neurologically
impaired, paralysed human beings. These implanted electrodes were
used to obtain sensory nerve signals suitable for controlling FES
systems designed to restore some basic hand or leg motor functions.
These nerve cuffs included a single circumferential electrode or a
single set of circumferential electrodes. These nerve cuffs were
incapable of selecting electrical signals arising from particular
nerve fibers in the nerve but instead recorded a signal reflecting
the aggregate electrical activity generated by all nerve fibers in
the nerve.
Useful sensory signals can be obtained using such single channel
electrodes. However, single channel electrodes have significant
disadvantages in some applications. For example, if it is desired
to record sensory signals originating from the nerves in one
particular digit with a single channel nerve cuff, it is necessary
to place the nerve cuff around a branch of the nerve which
originates in that digit before that branch joins nerve branches
which originate in other digits. Consequently, such single channel
nerve cuffs typically must be surgically implanted around very
small nerve branches in the fingers or hand. This requires
exacting, time consuming, surgical procedures. Furthermore, once
implanted, the small nerves and small nerve cuffs tend to be
fragile and, therefore, have a shorter life expectancy than would
be the case for a larger nerve cuff applied to a larger nerve.
Finally, nerve branches which originate at individual digits tend
to extend through relatively exposed places such as the palm of the
hand or wrist of a human being. This makes nerve cuffs applied to
such nerves even more susceptible to failure.
There has recently been increased interest in the use of nerve
cuffs having multiple sets of electrodes. Such multi-contact nerve
cuff electrodes may be applied above the point where branches of a
nerve combine into a main peripheral nerve trunk. At this point,
the nerve and the nerve cuff can be larger, and therefore, more
rugged. Furthermore, surgical implantation of a single larger nerve
cuff is easier and safer than implanting multiple small nerve cuffs
around individual smaller branches of the nerve.
When viewed in cross section, a typical nerve trunk comprises
several "fascicles" which are bundles of groups of nerve fibers.
Each fascicle contains a large number of nerve fibers or "axons".
Each fascicle is encircled by a protective sheath or "perineurium".
The fascicles are embedded in a relatively loose matrix of
connective tissue or "epineurium" which also contains a vascular
supply to the nerve. Blood vessels supplying the various fascicles
are highly interconnected in some anatomical locations. Nerve axons
frequently cross from one fascicle to another fascicle along the
course of a peripheral nerve.
The outer layers of epineurium are generally condensed into a
sheath (the "outer epineurial sheath") which encircles the nerve
trunk including all of its fascicles and internal blood supply. The
outer epineurial sheath delimits the nerve from surrounding
structures. A nerve trunk is typically only loosely attached to
adjacent anatomical structures by a conjunctival layer.
The outer epineurial sheath can be of variable thickness and
toughness. In some anatomical regions along the course of a nerve,
for example where fascicles are about to split off from a nerve
trunk to form separate nerve branches, the outer epineurial sheath
is very thin, the fascicles are not highly interconnected and the
fascicles are only loosely connected together by epineurium. In
other anatomical regions the outer epineurial sheath may be quite
thick and tough and the fascicles may be profusely interconnected
by multiple internal exchanges of axons and blood vessels.
Individual fascicles may originate, for example, from individual
digits in a person's hand. Ideally, each individual set of
electrodes in the multi-contact nerve cuff should stimulate, or
record activity from a single fascicle within a nerve trunk, or a
specific nerve within a nerve bundle. Because of the exchanges of
axons between fascicles, this ideal can not be achieved. There is a
need for cuff electrodes which can be used to approach this ideal.
Various designs have been proposed for multi-contact nerve cuffs.
All of these prior art designs have significant limitations in the
context of this intended use.
Some multi-contact nerve cuffs, for example, the nerve cuff
disclosed in Naples et al., U.S. Pat. No. 4,602,604 have multiple
sets of electrodes on the inner surface of a generally cylindrical
electrically insulating nerve cuff having a generally smooth
generally cylindrical inside surface. The Naples et al. nerve cuff
provides small windows cut through the inner surface of the cuff to
expose electrodes which are built into the cuff wall. Similar nerve
cuffs are shown in Grill et al. U.S. Pat. No. 5,505,201; Struijk et
al., Fascicle Selective Recording With a Nerve Cuff Electrode,
Proc. IEEE EMBS, Amsterdam, Netherlands, October, 1996; Sahin et
al. Selective Recording With a Multi-Contact Nerve Cuff Electrode,
Proc. of 19th Annual International Conference of IEEE EMBS,
Amsterdam, Netherlands, October, 1996 and Goodall,
Position-Selective Activation of Peripheral Nerve Fibres with a
Cuff Electrode, IEEE Trans. On Biomedical Engineering, Volume 43,
No. 8, August, 1996, p. 851. These basic designs for multi-contact
nerve cuffs have been used both for stimulation of individual
subpopulations of axons in a nerve trunk and for recording signals
that are generated by different sensor nerve fibre subpopulations
eg. axons located in different regions of a nerve trunk, that is
enclosed within a multi-contact nerve cuff.
An important problem which has been experienced with such
multi-contact nerve cuffs is lack of "selectivity", the ability to
identify signals from a particular one of many signal sources or
the ability to stimulate preferentially axons in one portion of a
nerve. For example, if it is desired to obtain a feed-back signal
originating from a single digit with a multi-contact nerve cuff
which is implanted around a portion of nerve which includes
branches extending to several digits, then it is difficult to
arrange the multi-contact nerve cuff so that one set of electrodes
produces an output signal which provides feedback only from the
selected digit and not from any other digit or digits.
One prior art method for achieving greater selectivity is to sew
fine wire electrodes into or around individual fascicles in a nerve
trunk. As the fine wire electrodes are each associated most closely
with a single fascicle in a nerve trunk or with a single nerve in a
nerve bundle, the fine wire electrodes can be very selective.
However, implanting such fine wire electrodes requires painstaking
surgery and, once implanted, the fine wire electrodes can fail
prematurely for various reasons.
Durand et al., U.S. Pat. No. 5,400,784 discloses another
multi-channel nerve cuff. The Durand et al. nerve cuff has
electrodes located on fin members. The fin members are attached to
spring members which are self-biased to slowly urge the fin members
to penetrate a nerve trunk at a predetermined rate. It is claimed
that the blunt fins in the Durand et al. nerve cuff slowly displace
fascicles in a nerve trunk rather than damaging them by piercing
the perineurium which encloses each fascicle. There is a concern,
however, that the Durand et al. nerve cuff may compress neural
tissues and thereby cause nerve damage as its electrodes are urged
into a nerve. Furthermore, while the Durand et al. nerve cuff may
be readily used in some anatomical locations (e.g. near points
where a nerve naturally splits into several branches and is
therefore no longer wrapped in tough outer epineurial sheath) the
Durand et al. nerve cuff is not well adapted for use in other
locations where the outer epineurial sheath is tough or where
individual fascicles in a nerve are profusely interconnected.
Tyler et al. U.S. Pat. No. 5,634,462 disclose a nerve cuff designed
to be placed around a nerve in a stretched configuration. The nerve
cuff has corrugations designed to slowly penetrate a nerve and to
carry electrodes into the nerve. The Tyler et al. cuff is still not
well adapted for use in anatomical locations where the outer
epineurial sheath is tough or where interconnections between
fascicles would be damaged by the penetrating corrugations.
Furthermore, the Tyler et al. cuff is not designed to provide an
effective seal around a nerve.
What is needed is a nerve cuff that can be used effectively to
selectively stimulate or record from targeted subpopulations of
nerve fibers in a nerve and can be used on nerves which could be
damaged by penetration.
SUMMARY OF THE INVENTION
This invention provides a multi-electrode nerve cuff which provides
good electrical isolation between individual electrodes or sets of
electrodes without actually penetrating a nerve. The nerve cuff
comprises an electrically insulating tubular cuff body penetrated
by a bore for receiving a nerve. A plurality of electrically
insulating ridges extend generally longitudinally on an inner
surface of the cuff body. The ridges project into the bore.
Adjacent pairs of the ridges define a plurality of parallel
chambers extending generally longitudinally in the bore. The ridges
electrically insulate adjacent chambers from each other. An
electrode or a set of electrodes is located in each of a plurality
of the chambers. The electrical isolation provided by the ridges
allows electrodes in different ones of the chambers to be used to
record electrical activity or to stimulate electrical activity
selectively in different regions of a nerve.
One embodiment of the invention provides a cuff in which the cuff
body comprises a plurality of linked segments. Each of the segments
comprising a cuff body portion bearing a longitudinally extending
blunt ridge member. Each segment spans a portion of a circumference
of the nerve cuff.
A second aspect of the invention provides a nerve cuff comprising a
fluid impermeable tubular cuff body penetrated by a bore for
receiving a nerve. The cuff body has a closure for permitting
passage of a nerve into the bore. A plurality of fluid impermeable
rounded ridges extend generally longitudinally on an inner surface
of the cuff body and project into the bore. Adjacent pairs of the
ridges define a plurality of chambers extending generally
longitudinally in the bore. One or more tubes extend into each of a
plurality of the chambers for introducing fluid into or withdrawing
fluid from the respective chambers. The ridges reduce the contact
between fluids in one of the chambers and portions of a nerve's
surface adjacent other ones of the chambers. Thus, the chambers
permit increased selectivity in both introducing fluids to specific
portions of a nerve or sampling fluids from adjacent specific
portions of a nerve.
A further aspect of the invention provides a method for
establishing a multi-channel interface with a nerve. The method
uses a nerve cuff comprising: a tubular cuff body penetrated by a
bore for receiving a nerve, the cuff body having a closure for
permitting passage of a nerve into the bore; and, a plurality of
longitudinal ridges extending generally longitudinally on an inner
surface of the cuff body and projecting into the bore, adjacent
pairs of the longitudinal ridges defining a plurality of chambers
extending generally longitudinally in the bore. The method involves
the steps of dissecting a nerve from surrounding tissues; opening
the closure and placing the cuff around the nerve with the chambers
extending along portions of the nerve; closing the closure, thereby
bringing the ridges into sealing contact with an outer surface of
the nerve without penetrating the outer surface of the nerve; and,
either stimulating selected portions of the nerve by introducing
electrical signals or pharmacological agents into selected ones of
the chambers or monitoring selected portions of the nerve by
measuring electrical potentials in the chambers or sampling fluids
from the chambers.
BRIEF DESCRIPTION OF THE DRAWINGS
Drawings which illustrate preferred embodiments of the invention
but which should not be construed so as to limit the scope of the
invention are appended in which:
FIG. 1A is a perspective view of multi-channel nerve cuff according
to a basic embodiment of the invention;
FIG. 1B is a perspective view of a nerve cuff according to an
alternative embodiment of the invention having circumferential
sealing ridges and four sets of tripolar electrodes;
FIG. 2 is a transverse sectional view of the cuff of FIG. 1B along
the lines 2--2;
FIG. 3 is a longitudinal sectional view of the cuff of FIG. 1B
along the lines 3--3;
FIG. 4 is a transverse sectional view of the nerve cuff of FIG. 1B
implanted around the sciatic nerve of a cat;
FIG. 5A is a sectional view of an alternative embodiment of the
invention having tubular sealing ridges in place around a
nerve;
FIG. 5B is a sectional view of the embodiment of FIG. 5A with the
nerve in a slightly expanded condition;
FIGS. 5C is a sectional view of an alternative embodiment of the
invention having tubular sealing ridges in place around a
nerve;
FIG. 5D is a sectional view of the embodiment of FIG. 5C with the
nerve in a slightly expanded condition;
FIGS. 6A and 6B are respectively transverse and longitudinal
fragmentary sectional views of a nerve cuff according to the
invention having fluid carrying tubes extending into a chamber
adjacent a nerve;
FIGS. 7A and 7B are perspective views of a nerve cuff according to
an alternative embodiment of the invention in unrolled and rolled
configurations respectively;
FIG. 8A is a perspective view of one segment from a multi-segmented
nerve cuff according to a further alternative embodiment of the
invention;
FIG. 8B is a sectional view showing a multi-segmented nerve cuff
comprising a plurality of connected segments encircling a nerve;
and,
FIG. 8C is a sectional view of a single channel nerve cuff
comprising a segment as shown in FIG. 8A retained by a flexible
band.
DETAILED DESCRIPTION
As shown in FIG. 1A a nerve cuff 20 according to the invention has
a tubular cuff body 24 which has an inner surface 22 enclosing a
generally cylindrical bore 25 for receiving a nerve. A closure 26
permits cuff body 24 to be opened, placed around a nerve, and
sealed with the nerve passing through bore 25.
Closure 26 is preferably a closure of the type described in
Kalles.o slashed.e et al., U.S. Pat. No. 5,487,756, which is
incorporated herein by reference. In general that closure comprises
a number of spaced apart first apertured members 26A affixed to
cuff body 24 at a first edge of a slit in the cuff body and a set
of one or more second apertured members 26B capable of being
interdigitated between first apertured members 26A and affixed to
cuff body 24 at a second edge of the slit. A thin flexible flap 32
is preferably provided to aid in sealing closure 26.
First apertured members 26A and second apertured members 26B have
apertures aligned generally with the slit. An elongated locking
member 27 can be inserted to extend through the apertures of first
apertured members 26A and second apertured members 26B when second
apertured members 26B are interdigitated with first apertured
members 26A. Locking member 27 may comprise, for example, suture
material or a semi-rigid rod.
A plurality of sealing ridges 28 (in the example of FIG. 1A, four
ridges 28 at 90 degree intervals around the circumference of bore
25) project inwardly into bore 25. Ridges 28 extend substantially
the entire length of cuff body 24. An open sided cavity or
"chamber" 30, which extends longitudinally along bore 25, is
defined between each pair of adjacent ridges 28. As described
below, when nerve cuff 20 is implanted around a nerve, then the
nerve closes the radially inwardly facing open sides of chambers
30. Ridges 28 provide electrical and/or fluid isolation between
adjacent chambers 30.
Nerve cuff 20 comprises an electrode 34 in each of a plurality of
chambers 30. Electrodes 34 may be used, for example, to selectively
electrically stimulate fascicles within a nerve (not shown in FIG.
1A) passing through bore 25.
FIGS. 1B, 2, 3 and 4 show a nerve cuff 20A according to an
alternative embodiment of the invention in which thin flexible
circumferential end sealing ridges 33 extend around bore 25 at each
end of ridges 28. Circumferential sealing ridges 33 help to enhance
the electrical and/or fluid isolation between different ones of
chambers 30 when nerve cuff 20A is implanted around a nerve. Nerve
cuff 20A has four groups of electrodes 34 which can each be used,
for example, to record electrical activity in a nerve N (FIG. 4)
passing through bore 25.
Cuff body 24 comprises a biocompatible material, such as a
biocompatible silicone. Where a nerve cuff is to be used for
electrical measurements or stimulation the material of the cuff
body 24, including ridges 28 and 33, should be electrically
insulating. Ridges 28 and 33 may also be formed from silicone.
Ridges 28 and 33 should be blunt, are preferably rounded, and most
preferably have generally semi-circular cross-sectional profiles,
as shown best in FIGS. 2 and 3.
Ridges 28 and 33 preferably comprise a soft fluid impermeable
material, such as a soft silicone which will gently seal against
the outer epineurial sheath of a nerve trunk without penetrating or
excessively indenting the outer epineurial sheath. Ridges 28 and 33
may be formed integrally with cuff body 24 or may comprise separate
elements affixed to cuff body 24.
FIG. 4 shows a cuff 20A in place around a nerve N. Nerve N has a
number of fascicles F1, F2, F3, F4 and F5 and is surrounded by a
outer epineurial sheath E. It can be seen that each chamber 30 is
closed on all sides. Ridges 28 and 33 press against the outer
epineurial sheath E of nerve N sufficiently to provide a fluid seal
against nerve N. Ridges 28 do not penetrate the epineurial sheath E
of nerve N. Each chamber 30 is closed by a pair of ridges 28 on
either side, a portion of the inner wall 22 of cuff body 24 on the
outside, and a portion of the surface of nerve N on the inside. In
the embodiment of FIGS. 1B, 2, 3 and 4, portions of circumferential
sealing ridges 33 help to better seal chambers 30 on each end.
FIGS. 5A and 5B show a nerve cuff 20B according to an alternative
embodiment of the invention having tubular ridges 28A. Ridges 28A
are formed from soft pliable silicone material. The walls of ridges
28A preferably have a thickness in the range of 0.05 mm to 0.25 mm
and a hardness of about durometer 30 or less. Ridges 28A are in the
form of hollow hemi cylinders having an outside radius of curvature
of about 0.2 mm to about 0.5 mm. Each ridge 28A has a longitudinal
channel 29. Channels 29 are preferably open at their ends so that
body fluids can flow into or out of channels 29 with local changes
in fluid pressure.
Ridges 28A may be formed, for example, from lengths of medical
grade silicone tubing. The tubing may have an external diameter in
the range of about 0.5 mm to 1 mm. Lengths of the tubing can be
longitudinally split in half and then affixed in bore 25 with a
suitable silicone adhesive. Ridges 28A could also be formed
integrally with cuff body 24.
As shown in FIG. 5B, ridges 28A can seal against nerve N and yet
can deform to accommodate slight expansions in nerve N without
penetrating or significantly indenting nerve N. Tubular ridges 28A
may be used with any of the embodiments of nerve cuff described
herein.
FIGS. 5C and 5D show a nerve cuff 20C having hollow cylindrical
longitudinal ridges 28B according to another embodiment of the
invention. Ridges 28B may comprise, for example, lengths of 0.5 mm
external diameter medical grade silicone tubing adhesively affixed
to the internal walls of cuff 20C. The tubing should have thin
walls which allows it to conform well to the surface profile of a
nerve N. Nerve cuff 20C functions in substantially the same manner
as nerve cuff 20B of FIGS. 5A and 5B.
Nerve cuffs according to the invention may be used to selectively
record electrical signals or other electrical characteristics from
portions of a nerve N, to selectively electrically stimulate
certain portions of a nerve N, to selectively expose portions of a
nerve N to chemical or pharmacological agents or to selectively
monitor the compositions of fluids surrounding certain portions of
a nerve N.
Cuffs 20 and 20A of FIGS. 1A and 1B through 4 are equipped with
electrodes 34 for selectively electrically stimulating a nerve N or
for selectively recording electrical activity in portions of nerve
N. Those skilled in the art will understand that various
configurations and numbers of electrodes 34 may be placed in
chambers 30 in cuffs according to the invention. In multi-channel
nerve cuffs according to the invention, electrodes 34 (or sets of
electrodes 34) are located in two or more of chambers 30.
Electrodes 34 are in electrical contact with fluids in chambers 30.
It is not necessary for electrodes 34 to contact a nerve N passing
through bore 25. Electrodes 34 are electrically connected to
external equipment (not shown) by insulated wires 35. Wires 35 may
be may be embedded in cuff body 24 or routed on the outside or
inside of cuff 20. If wires 35 are external to a nerve cuff then
wires 35 may pass through a sleeve 50 attached to the nerve cuff
(as shown in FIGS. 1A and 1B). In the alternative, electrodes 34
may be connected to miniature amplifiers located in or near the
cuff and signals may be transmitted to or from external equipment
using radiotelemetry or other wireless means.
In the embodiment of FIG. 1A, each chamber 30 has a single
electrode 34. In cuff 20A of FIGS. 1B through 4, a set of three
electrodes 34 are located in a balanced tripolar configuration in
each chamber 30. Cuff 20A is well adapted for nerve recording
applications. Electrodes 34 are equally spaced and centered between
ridges 28 in chambers 30. In typical nerve recording applications
nerve cuff 20A could be about 10 mm to 50 mm long and electrodes 34
could be spaced apart by up to about one half of the length of cuff
20A.
Electrodes 34 may be connected so that those electrodes 34A (FIG.
3) nearest the opposing ends of each chamber 30 are shorted
together. The center electrode 34B can be connected to measuring
equipment for measuring nerve action potentials relative to an
electrical potential of the two outermost electrodes 34A. Of
course, other configurations of electrodes 34 could be placed in
chambers 30. Each chamber 30 may have more or fewer than three
electrodes 34.
A nerve cuff adapted for nerve stimulation applications could
comprise, for example, two electrodes 34 in each chamber 30
separated longitudinally inside the chamber. A large variety of
numbers and arrangements of electrodes 34 could be used for nerve
stimulation.
The dimensions of a nerve cuff according to the invention will vary
depending upon the size of the nerve to which the nerve cuff will
be applied. The cuff should be dimensioned so that ridges 28 gently
but sealingly contact the outer epineurial sheath of the nerve. For
example, a typical nerve cuff for implantation about the sciatic
nerve of a cat has a length of about 25 mm and a bore 25 of about
3.5 mm in diameter. A typical nerve cuff for implantation about the
median or ulnar nerve of a cat forelimb has a length of about 15 mm
and a bore 25 of about 2.5 mm in diameter. Ridges 28 typically
project about 0.25 mm to 0.5 mm into bore 25. Ridges 28 typically
project into bore 25 by approximately 5% to approximately 20% of an
internal diameter of bore 25.
Instead of, or in addition to, making electrical contact with a
nerve, a nerve cuff according to the invention could be used to
selectively expose portions of a nerve to pharmacological agents or
other chemicals or to selectively sample fluids adjacent to
portions of the surface of a nerve. In such applications,
electrodes 34 are replaced with, or augmented by, one or more tubes
42 connected to deliver or remove small amounts of fluid to
chambers 30.
FIGS. 6A and 6B show transverse and longitudinal fragmentary
sectional views of a nerve cuff having tubes 42 connected to
deliver fluid into (or remove fluid from) a chamber 30 through
openings 44. Ridges 28 prevent fluids from one chamber 30 from
moving into an adjacent chamber 30. Most preferably two tubes 42
extend into a chamber 30 at longitudinally spaced apart locations.
A small amount of fluid can be introduced into chamber 30 via one
of the tubes 42 while an equivalent amount of fluid is removed
through the other tube 42. Providing two tubes 42 near opposing
ends of chamber 30 permits pharmacological agents or other
chemicals to be flushed from chamber 30.
FIGS. 7A and 7B illustrate a nerve cuff 120 according to a further
alternative embodiment of the invention. Nerve cuff 120 comprises a
self-curling sheet 124 biased to curl upon itself around an axis
115 to form an annular nerve cuff having a bore 125. A nerve can be
inserted through bore 125 by unrolling sheet 124 and then
permitting sheet 124 to curl around a nerve in a controlled manner.
Nerve cuffs of this general type are described in Naples et al.,
U.S. Pat. No. 4,602,604. A plurality of rounded ridges 128 extend
along sheet 124 in a generally longitudinal direction.
When nerve cuff 120 is in its curled up configuration, as shown in
FIG. 7B, ridges 128 project into bore 125 and function in the same
manner as ridges 28 and 28A, which are described above, to define
chambers 130 between cuff 120 and a nerve N passing through bore
125. Electrodes 134 suitable for nerve stimulation and/or recording
may be provided on sheet 124 between ridges 128. In the
alternative, fluid conduction means, such as tubes, may be provided
to conduct fluids into or out of chambers 130.
FIGS. 8A and 8B illustrate a modular nerve cuff 220 according to
the invention. Nerve cuff 220 comprises several segments 221. Each
segment 221 comprises elements of a closure 226 which allows each
segment 221 to be attached to adjacent segments 221. Each segment
221 comprises a flexible body wall portion 224 and a longitudinal
ridge 228. When several segments 221 are assembled to form a cuff
220, as shown in FIG. 8B, then pairs of adjacent ridges 228 define
chambers 230 between themselves. Ridges 228 and chambers 230
function in substantially the same manner as ridges 28 and chambers
30 described above. Each chamber 230 may bear one or more
electrodes 34 and/or one or more fluid carrying tubes 42.
Transverse end sealing ridges (not shown) may optionally be
provided along the end edges of segments 221.
Closures 226 are preferably of the type described above. Each cuff
segment 221 bears along its longitudinal edges sets of closing
elements 226A and 226B. Elements 226A and 226B may be
interdigitated and secured with a suitable locking member 227.
Preferably, as shown in FIG. 8A, each segment 221 has a curved
longitudinal flap 229 extending along a first lateral edge inwardly
adjacent to members 226A. Flap 229 is preferably bonded to members
226A and seals its closure 226. In each segment 221, ridge 228
preferably comprises a curved flap extending along a second lateral
edge of segment 221. Flaps 228 and 229 may be fabricated, for
example, from longitudinally bisected lengths of silicone tubing or
may be formed integrally with bodies 224 of cuff segments 221 by
any suitable process.
As shown in FIG. 8B, when a closure 226 is closed then flaps 228
and 229 overlap along their lengths. The flap which defines ridge
228 is preferably spaced apart from flap 229 so that it can move to
better conform to the outer surface of a nerve N. Longitudinal
ridges 228 press against the outer epineurial sheath of a cuffed
nerve N, as described above, to provide a fluid seal against nerve
N.
Nerves are typically not circular in cross-section. The modular
embodiment of FIGS. 8A and 8B is particularly well adapted for
cuffing nerves having non-circular cross-sections. The widths of
the modular cuff segments 221 may vary. In some applications it may
be desirable to have some narrow segments 221 defining narrow
chambers 230 and some wider segments 221 defining wider chambers
230 to better match the local anatomy of the nerve.
The modular embodiment of FIGS. 8A and 8B offers the advantages
that a cuff having a desired combination of electrodes and/or tubes
can be made from segments 221 equipped with different combinations
of electrodes 34 and/or tubes 42. The sizing of cuff 220 can be
adjusted by replacing any one or more of segments 221 with a
segment 221 having a different width. It is advantageous that a
cuff 220 can be readily custom fitted by a surgeon who is
implanting cuff 220. During implantation, while nerve N is exposed,
the surgeon can select segments 221 from a set of segments 221 of
graduated widths to provide a cuff 220 which is well fitted to
nerve N.
FIG. 8C is a transverse sectional view of a nerve cuff 220A
comprising a single segment 221 held in place on a nerve N by means
of a flexible band 290 that encircles nerve N and attaches to
either side of segment 221. Band 290 may take the form of a wide
segment 221. Band 290 may be perforated or apertured. This
embodiment provides a single chamber 30 covering a limited region
of the surface of nerve N between two ridges 228. One or more
electrodes 34 and/or one or more fluid carrying tubes may
communicate with the interior of chamber 30.
Those skilled in the art will appreciate that nerve cuffs according
to this invention can provide better selectivity for activity in
selected portions of a nerve than conventional nerve cuffs because
of ridges 28, which divide the volume inside the nerve cuff and
exterior to a nerve passing through the nerve cuff into a number of
chambers 30 which are insulated from each other. This result is
achieved without the need to penetrate the outer epineurial sheath
of the nerve and without the risk of harm that such penetration
could cause. A nerve cuff according to the invention may be used in
anatomical areas where penetration type nerve cuffs could not be
used because the outer epineurial sheath is too tough to allow
penetration or because penetration would excessively damage the
nerve.
As will be apparent to those skilled in the art in the light of the
foregoing disclosure, many alterations and modifications are
possible in the practice of this invention without departing from
the spirit or scope thereof. For example, if a nerve cuff is
sufficiently long then circumferential sealing ridges 33 may not be
required in some applications. The dimensions and shape of the
profile of ridges 28 and 33 may be varied from the shapes shown in
the drawings as long as these ridges can seal against a nerve well
enough to divide the space within the cuff and around the nerve
into two or more isolated chambers and yet remain sufficiently soft
and blunt that they do not damage the nerve passing through bore 25
by penetration or excessive indention. Chambers 30 need not extend
along the entire length of cuff 20. The configurations of
electrodes and/or fluid carrying tubes in chambers 30 may be
varied. Accordingly, the scope of the invention is to be construed
in accordance with the substance defined by the following
claims.
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